We'll be using the Dell Perc 5i controller, which is a SAS/SATA controller and is on the VMWare storage HCL.
Does this mean I can use it as storage for a guest OS, or can I install ESX onto the SATA device? Both? We'll be using ESX 3.5 update 1 or newer, latest patch level.
You will be able to install ESX onto the drive. You should also be able to configure a VMFS volume on the disk as they are presented as SCSI... not sure about both at the same time though.
There is some info here which may assist you: